Are the average carbon dioxide concentrations in cloth and surgical masks high enough to potentially impair certain brain functions?
A study published in 2021 by the journal Aerosol and Air Quality Research measured CO2 levels in the breathing zones of a surgical mask and a 3-layer cloth mask. The study found that the average CO2 concentration was 2,051 parts per million (ppm) in the cloth mask and 2,107 ppm in the surgical mask. The study was conducted in a well-ventilated lab with CO2 levels close to that of fresh air (400 ppm). CO2 levels in classrooms are commonly more than twice that of fresh air, which can push the CO2 concentrations in the masks to much higher levels. A study published by the journal Environmental Health Perspectives in 2012 found that CO2 levels of 2,500 ppm cause "large and statistically significant reductions" in high-level brain functions like initiative, strategic thinking, and complex decision-making. A study published by the journal Nature in 2018 found similar results. The CO2 levels in N95 masks commonly worn in hospitals are far higher, ranging from 13,000 to 35,000 ppm.